Traditional scenario of the 'Millionaire problem':

Let's say there are 5 individuals named Jon, Vincent, Kale, Trevor and Bob. Jon, Vincent, Kale and Trevor (JVKT for short) are all millionaires and live a wealthy life. The JVKT millionaires are rather rich but don't know who's the richest of them all. However, they don't want to show each other how much they each specifically have. That's where Bob comes in. Let's say Bob is incorruptable and therefore unbribable and will always supply the correct answer and never leak data. Learn More

The exact same scenario as before now takes place, but instead of using Bob to compute the data we'll use a mathmatically proven and secure protocol called Secure Multi-Party Computation to compute the answer. The JVKT millionaires now each make an individual dataset composed out of their own account balance numbers. Each millionaire locks their dataset with their own 'key' encrypting the dataset. This key is derived from a sort of 'master-key', but I'll go in further detail about that later on. Learn More